JPS5896829A - Purifying method for metal - Google Patents

Abstract

PURPOSE:To recover metal having high purity effectively by immersing the cooled surface for crystallization of metal into molten metal, and moving the same upward from the molten metal while pressurizing the metal crystallized on said surface with rotating rolls. CONSTITUTION:The lower parts of cooled horizontal rolls 2 of which a pair of opposed surfaces move and rotate upward are immersed in, for example, molten Al 1 which is controlled of temp. to the neighborhood of the liquidus line in a molten metal well 5. Purifed Al3 is crystallized on the lower surfaces of the rolls 2 and in the state of removing the purified Al upward from the molten metal 1 by the rotation of the rolls 2, the same is compressed by the pressure exerted between the rolls 2. The half molten part separated from the solid phase by the compression is returned into the molten metal. In order to prevent oxidation of the Al, etc. the surface of the metal 1 is preferably kept in an inert gaseous atmosphere of N2, etc. The strip-like purified Al removed upward from the metal 1 is cut with a shear 7 via pinch rolls 6 to a cut plate or is coiled with a coiler 8 to a product.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying metals. Specifically, the present invention relates to a method for obtaining a highly pure plate metal from a metal containing impurities by a fractional crystallization method.

Conventionally, various methods have been proposed as methods for purifying metals, particularly for purifying aluminum, and some of them have already been adopted industrially. For example, the three-layer electrolytic method and the fractional crystallization method are known as methods for obtaining aluminum with a purity of about the same level as Tade, and the methods for purifying aluminum scrap include the rotational crystallization method, the Zinkal method, and the B
Eck (Peck) method, precipitation separation method, etc. have been proposed. However, none of these methods are economically advantageous, and some of them have drawbacks such as low purification efficiency, and are not industrially sufficient.

The inventors of the present invention have made intensive studies to solve the drawbacks of these conventional methods and find an industrially advantageous metal purification method. As a result, by combining a fractional crystallization process and a mechanical squeezing process, The present invention was achieved by discovering that metals with extremely high purity can be efficiently recovered.

That is, an object of the present invention is to provide an industrially advantageous metal purification method, and the purpose is to immerse a cooled surface for metal crystallization into molten metal maintained near the liquidus line. This can be easily achieved by crystallizing the metal on a surface, then moving the crystallized surface above the molten metal while applying pressure with a rotating roll, and recovering the crystallized metal while squeezing it. .

The present invention will be explained in detail below when applied to the purification of aluminum.

In the present invention, first, a cooled surface for metal crystallization is immersed in molten aluminum maintained near the liquidus line, and aluminum is crystallized on the surface. In this aluminum crystallization process, solute components such as elements that form a eutectic with aluminum, such as iron, manganese, silicon, magnesium, zinc, copper, nickel, and gallium, are first extracted using the solute distribution effect during crystallization. Separate from crystalline aluminum.

At this time, in order to increase the separation efficiency (l-/..), C
BAco, therefore ke calculated by the following formula (2)
needs to be made smaller. 4, it becomes important to reduce the crystallization rate (R) and the boundary layer thickness d).

-P' by θ-1%. =ks(/s)・・・・・・・・・
・・・・・・・・・・・・(1) Specifically, the crystallization rate (R
) is achieved by controlling the temperature of the molten aluminum and the surface for metal crystallization to such an extent that the amount of heat removed from the molten aluminum slightly exceeds the amount of heat input. If the crystallization rate becomes too low, productivity will be adversely affected, so in actual operation, the crystallization rate is controlled to be kept within a suitable range in consideration of productivity and separation efficiency. The boundary layer thickness d) can be reduced by sufficiently stirring the liquid phase side of the solid-liquid interface, that is, the molten aluminum. Particularly when aluminum scrap with a high concentration of impurities is used as a raw material, local non-uniformity of components occurs at the solid-liquid interface, which tends to reduce the purity of the resulting aluminum, so it is especially important to stir the molten metal efficiently. desired.

In the crystallization process, the aluminum crystallized on the surface for metal crystallization is pressed by rotating rolls and moved above the molten aluminum to compress it. By adding , the degree of purity is further increased. That is, normally, the solid phase separated from the molten metal by fractional crystallization as in the crystallization process of the present invention contains pure aluminum and some impurities (solute components), which form eutectic with aluminum. At the crystallization temperature during crystallization, it is in a semi-molten state.

Therefore, the purity of the aluminum obtained is increased by separating this semi-molten eutectic portion from the solid phase by mechanical compression.

Next, the present invention will be explained in more detail with reference to FIGS. 1 to 3, which show examples of embodiments of the present invention.

FIG. 1 is a schematic vertical sectional view showing an example of a purified metal recovery apparatus suitable for carrying out the present invention. In Fig. 1, a pair of cooled aluminum melts (1) whose temperature is controlled near the liquidus line in a molten metal reservoir (5) are rotated in such a direction that a pair of opposing surfaces move upward. Horizontal roll (2)
The lower part of the roll is immersed to crystallize purified aluminum (3) on the lower surface of the roll. There is no particular restriction on the method of cooling the horizontal roll (co), and an external cooling method, an internal cooling method, or the like may be adopted. For example, as shown in Fig. 2 (a), there is a method in which cooling gas is sprayed from a supply nozzle (/l) onto the upper surface of a horizontal roll (Fig. 2); A cooling roll (a method of cooling by bringing it into contact with the grapes, or a roll (2) as shown in Figure 1 (C))
Examples include a method of providing a cooling medium inlet pipe (/3) and an outlet pipe (/3) inside the roll and supplying cooling gas or cooling liquid to the inside of the roll for cooling.

Purified aluminum (
The three cylinders are squeezed by the pressure applied between the rolls as they are removed upward from the molten metal by rotation of the rolls.

Here, the semi-molten portion separated from the solid phase by compression is returned to the molten metal by sedimentation due to gravity or diffusion due to concentration difference. The rotational speed of the roll (2) is easily determined experimentally or empirically depending on the molten metal composition, the roll diameter, the desired plate thickness and its purity, etc. ``The material of the roll is not particularly limited, but it is desirable that it does not contaminate the molten metal, has good thermal conductivity, and has heat resistance and durability. Generally, steel or carbon-lined steel is suitable. be.

Note that the surface of the molten metal is preferably kept in an inert gas atmosphere such as nitrogen or argon in order to prevent oxidation of aluminum or the solute components contained therein. Furthermore, although stirring of the molten metal is not essential, it is desirable to stir the molten metal in order to increase the degree of purity. As shown in Figure 1, methods for stirring the molten metal include rotating a stirring blade inserted into the molten metal, releasing fine bubbles from the lower part of the molten metal reservoir, and stirring the molten metal using electromagnetic force. Examples include a method of rotating the object, or a method of combining these methods. The band-shaped purified aluminum that has been taken out upward from the molten metal and squeezed between rolls passes through pinch rolls (6) and then shears (7).
The product is either cut into a cut plate using a machine, or wound into a coil using a winding machine.

FIG. 3 is a schematic vertical sectional view showing another example of a purified metal recovery apparatus suitable for carrying out the present invention. In Figure 3(a), molten aluminum (21) whose temperature is controlled near the liquidus line
A cooled plate (22) is immersed therein, and purified aluminum (3) is crystallized on the surface of the plate. There are no particular restrictions on the method of cooling the plate (1), but examples include a method of cooling the plate by supplying cooling gas once through the longitudinally rotating medium supply nozzle (3/) of the plate, as shown in Figure 1. . Note that the cooling medium is not limited to gas, but may be liquid as long as a discharge path is secured.

The purified aluminum (3) that has crystallized on the surface of the plate (〃) is pulled upwards at the same time as the plate is pulled up by a pair of bidirectional rolls installed horizontally above the molten metal. It is squeezed by the pressure applied by (2W).

The type of roll (42g') is not particularly limited, but a self-rotating roll is preferred. The materials of the roll (2St) and the plate (1) are not particularly limited, but steel or carbon-lined steel is preferred for the same reason as the material of the roll (co) in the apparatus shown in FIG. 1 described above. The semi-molten portion separated by squeezing is returned to the molten metal as in FIG.

In this case as well, it is desirable to stir the molten metal using a stirring blade (two) or the like or to create an inert gas atmosphere on the surface of the molten metal in order to obtain purified aluminum with high purity.

In this method of crystallizing purified aluminum on the plate surface using a cooled plate, the plate is repeatedly raised and lowered without recovering the crystallized metal.
Productivity can also be improved by repeating crystallization and compression of purified aluminum several times to crystallize multiple layers of purified aluminum on the surface of the plate. In this case, it is important to control the interval between the rolls (2W) according to the layer thickness of purified aluminum.

The plate-shaped purified aluminum that has been taken out upward from the molten metal and compressed between rolls is then used in a surface-forming machine.

According to the present invention, by efficiently combining metal crystallization and compression, purified metal can be recovered continuously or semi-continuously, and productivity and workability are excellent, so it is economical. It is also extremely advantageous.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view showing an example of a purified metal recovery apparatus suitable for implementing the present invention, and FIG. 2 is a diagram showing an example of a method for cooling the horizontal roll of the apparatus of FIG. Figure 2 (a
) is a method of blowing cooling gas onto the roll surface, Figure 2 (
b) is a method using a separately provided cooling roll, as shown in Figure 2 (
C) shows a method of supplying a cooling medium inside the roll. FIG. 3 is a schematic vertical cross-sectional view showing another example of a purified metal recovery apparatus suitable for carrying out the present invention, and FIG. (b) shows the state in the process of moving the plate above the molten metal. FIG. 9 is a longitudinal sectional view showing an example of a method for cooling the plate material of FIG. 3. In the figure, /, 2/...molten aluminum, ko...horizontal roll, 3, +23...purified aluminum, ri, 25...
[t' wing m, g... pinch roll, 2... shear,
! ...winding machine, //...supply nozzle, /2...
・Cooling roll, /3...Cooling medium introduction pipe, 22...
・Plate body, λri...roll, 3/...cooling medium supply nozzle. 2nd Nagi (c) (α) (?) 4th Σ

Claims (1)

[Claims] (1) A cooled metal crystallization surface is immersed in molten metal maintained near the liquidus line to crystallize the metal on the surface,
A method for purifying a metal, which comprises: then moving the surface of the crystallized metal above the molten metal while pressurizing it with a rotating roll, and recovering the crystallized metal while squeezing it. (2. In the metal purification method described in claim 1, the surfaces of a pair of horizontal rolls that rotate in such a direction that the opposing surfaces move upward are used as metal crystallization surfaces, and the rolls A method characterized by immersing the lower part of the roll in molten metal, and moving the metal crystallized substance crystallized on the lower surface of the roll upward while being squeezed by pressure applied between the rolls. (3) In the metal purification method according to claim 7, the surface of the plate is used as a surface for metal crystallization, and the plate is immersed in molten metal and then pulled up. A method characterized in that the metal crystallized material is moved upward while being squeezed by pressure applied between a roll provided above the molten metal and the plate. Any one of range 7 to 3
The method for purifying a metal according to item 1, which comprises stirring the molten metal. (5) Any one of claims 1 to 7
The method for purifying a metal according to item 1, characterized in that the surface of the molten metal is placed in an inert gas atmosphere.